Optical device that produces flicker-like optical effects

ABSTRACT

An optical device that produces flicker-like optical effects is provided. The inventive device employs directionally cured image icons. Specifically, the optical device is made up of at least one arrangement of image icons formed from one or more cured pigmented materials, and at least one arrangement of optionally embedded focusing elements positioned to form one or more synthetic images of at least a portion of the arrangement(s) of image icons. Some or all of the pigmented material(s) is cured using collimated light directed through the focusing elements toward the arrangement(s) of image icons at one or more angles relative to a surface of the optical device to form directionally cured image icons. The synthetic image(s) of the directionally cured image icons is viewable at the cure angle(s) and therefore visually appears and disappears, or turns on and off, as the viewing angle of the device moves through the cure angle(s).

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of application Ser. No. 15/129,438,which is the National Stage of International Application No.PCT/US2015/022907, filed Mar. 27, 2015, which claims priority to UnitedStates Provisional Patent Application No. 61/971,240, filed Mar. 27,2014, the disclosures of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention generally relates to an optical device thatproduces flicker-like optical effects, and more particularly relates toan optical device that employs directionally cured image icons.

BACKGROUND

Micro-optic film materials projecting synthetic images generallycomprise: an arrangement of micro-sized image icons; an arrangement offocusing elements (e.g., microlenses, microreflectors); and optionally,a light-transmitting polymeric substrate. The image icon and focusingelement arrangements are configured such that when the arrangement ofimage icons is viewed using the arrangement of focusing elements, one ormore synthetic images are projected. The projected images may show anumber of different optical effects.

These micro-optic film materials may be used as security devices forauthentication of banknotes, secure documents and products. Forbanknotes and secure documents, these materials are typically used inthe form of a strip, patch, or thread and can be partially embeddedwithin the banknote or document, or applied to a surface thereof. Forpassports or other identification (ID) documents, these materials couldbe used as a full laminate or inlayed in a surface thereof. For productpackaging, these materials are typically used in the form of a label,seal, or tape and are applied to a surface thereof

Examples of micro-optic film materials are described and shown in U.S.Pat. Nos. 7,333,268 and 7,468,842. These references both describe amicrostructure approach to forming image icons, in which the image iconsare formed from voids in a microstructure or from solid regions, singlyor in combination. The voids are optionally filled or coated with amaterial having a different index of refraction than the surrounding orunderlying material, a dyed material, a metal, or a pigmented material.Such an approach has the benefit of almost unlimited spatial resolution.

SUMMARY

An exemplary method of manufacturing these micro-optic film materials isto form the icons as voids in a radiation cured liquid polymer that iscast against a base film, such as 75 gage adhesion-promoted polyethyleneterephthalate (PET) film, then to form the lenses from radiation curedpolymer on the opposite face of the base film in correct alignment orskew with respect to the icons, then to fill the icon voids with asubmicron particle pigmented coloring material by gravure-like doctorblading against the film surface, solidify the fill by suitable means(e.g., solvent removal, radiation curing, or chemical reaction), andfinally apply an optional sealing layer that may be either clear, dyed,pigmented, or incorporate covert security materials. Here, the means forsolidifying the fill is non-directional and applied directly to theimage icon layer and not through the lenses. Synthetic images of suchnon-directionally cured icons are viewable over a wide range of angles.

The icon voids may include multiple icon fill materials. For example, incol. 49, lines 36-63, of U.S. Pat. No. 7,468,842, icon voids areunderfilled with a first icon fill material, and optionally stabilized(e.g., by radiation curing). The icon voids are then optionally filledwith a second icon fill material. In this example, the icon fillmaterial is stabilized by non-directional techniques such asnon-directional curing that is applied directly to the icon fillmaterial and not through the lenses.

Another example of a micro-optic film material is known from U.S. Pat.No. 7,738,175. This reference discloses a synthetic micro-optic systemthat produces a flicker-like optical effect. The system produces anin-plane image formed from an array or pattern of image icons and anarray of focusing elements. Here, the in-plane image is defined as animage that has some visual boundary, pattern, or structure that visuallylies substantially in the plane of the substrate on which or in whichthe in-plane image is carried. The system also produces at least oneout-of-plane synthetic image, the out-of-plane synthetic image(s)operating to modulate or control the extent of the appearance of thein-plane synthetic image. In one embodiment, the out-of-plane syntheticimage serves to control the field of view of the in-plane image and,thus, serves to modulate or control the extent of appearance of thein-plane image. Here, the appearance of the in-plane image visuallyappears and disappears, or turns on and off, depending upon the viewingangle of the system.

By way of the present invention, it has been discovered thatdirectionally curing the image icon layer of these film materialsthrough the lens layer using collimated light greatly increases therange of optical effects demonstrated by these materials.

The present invention therefore provides an optical device that producesflicker-like optical effects, wherein the optical device comprises atleast one arrangement of image icons formed from one or more curedpigmented materials, and at least one arrangement of optionally embeddedfocusing elements positioned to form one or more synthetic images of atleast a portion of the arrangement(s) of image icons, wherein some orall of the pigmented material(s) is cured using collimated lightdirected through the focusing elements at one or more angles relative toa surface of the optical device (hereinafter “the cure angle(s)”) toform directionally cured image icons, wherein the synthetic image(s) ofthe directionally cured image icons is viewable at the cure angle(s) andtherefore visually appears and disappears, or turns on and off, as theviewing angle of the device moves through the cure angle(s).

The term “pigmented material”, as used herein, is intended to mean anymaterial capable of imparting a color to the image icons and to thesynthetic image(s) of the inventive device, which is curable bycollimated light. In one contemplated embodiment, the pigmented materialis a curable pigment dispersion (i.e., pigment particles in a curablemedium or carrier).

As will be explained in more detail below, the synthetic image(s)projected by the inventive optical device may demonstrate a number ofdistinct visual effects when the device is tilted about an axissubstantially parallel to the plane of the device. For example, thesynthetic image(s) may show orthoparallactic movement (OPM) (i.e., whenthe device is tilted the images move in a direction of tilt that appearsto be perpendicular to the direction anticipated by normal parallax).Unlike the prior art micro-optic system described above that produces aflicker-like optical effect, the image(s) projected by the presentinvention is not necessarily an image that visually lies substantiallyin the plane of the device but may also appear to rest on a spatialplane that is visually deeper than the thickness of the device, or mayappear to rest on a spatial plane that is a distance above the surfaceof the device. The image(s) may also appear to oscillate from a positionabove the device to a position below the device, or the reverse, as thedevice is rotated through a given angle (e.g., 90 degrees), thenreturning to its original position as the device is further rotated bythe same amount.

The image icons of the inventive device, which are prepared using one ormore cured pigmented materials, may be made in the form of posts, or inthe form of voids or recesses on or within a surface of the inventiveoptical device. The posts may be formed from the pigmented material(s),or the areas surrounding the posts or the voids or recesses may beeither coated or partially or completely filled with the pigmentedmaterial(s). The size, form and shape of the icons are not limited. Infact, embodiments are contemplated in which two or more types of imageicons (e.g., micro- and nano-sized image icons) are in register with oneanother within one arrangement or layer of image icons within theinventive device.

In one exemplary embodiment, each image icon in the arrangement(s) ofimage icons is formed from one cured pigmented material, the pigmentedmaterial being cured using collimated light at a given angle. In thisembodiment, the synthetic image(s) is viewable at the cure angle. Inother words, the projected synthetic image(s) flickers or turns on andoff, as the viewing angle of the device moves through the cure angle.

Image icons formed from two or more pigmented materials may be preparedby curing each material with collimated light, or by curing one materialwith collimated light and another material with another means for curing(e.g., non-directional radiation curing, chemical reaction). Syntheticimages formed from the directionally cured pigmented materials would beviewable at the cure angle(s), while synthetic images formed from thenon-directionally cured pigmented materials would be viewable over awide range of angles. It is noted that the arrangement(s) of image iconsused in the practice of the present invention may also include prior artimage icons formed in their entirety from non-directionally curedpigmented materials.

In one such exemplary embodiment, each image icon in the arrangement(s)of image icons is formed from two cured pigmented materials, each havinga different color. Each pigmented material is cured using collimatedlight at an angle through the focusing elements that is different fromthe angle used to cure the other pigmented material. The optical device,in this exemplary embodiment, will project a synthetic image(s) of afirst color that is viewable at the first cure angle, and a syntheticimage(s) of a second color that is viewable at the second cure angle.

This exemplary embodiment can be produced by curing a colored pigmentedmaterial using collimated light from one angle, washing the uncuredpigmented material from the device, and then adding a second coloredpigmented material and curing it. As will be readily appreciated, alarge number of colored pigmented materials could be added this way.

In another such exemplary embodiment, each image icon in thearrangement(s) of image icons is formed from one cured fluorescentpigmented material and from one cured non-fluorescent pigmentedmaterial. As will be readily appreciated, a fluorescent feature that isdetectable only at a given angle but not at another given angle mayserve as an effective machine readable authenticating feature.

In a preferred embodiment, the inventive optical device is used with anID card having one or more security print features (e.g., text, photo).The security print feature(s) would be visible at select viewing angleswhile the synthetic image(s) projected by the inventive device would bevisible at other select viewing angles. In this way, the syntheticimage(s) would not obscure or impair the security print feature(s).

In a further exemplary embodiment, the inventive optical device is alaser marked optical device that basically comprises an optical deviceas described above (e.g., an optical film material), and optionally oneor more layers located above and/or below the optical device, wherein atleast one arrangement or layer of the optical device or at least onelayer above or below the optical device is a laser markable arrangementor layer, and wherein the laser markable arrangement(s) or layer(s) hasone or more laser marked static two dimensional (2D) images thereon.

The present invention further provides sheet materials and baseplatforms that are made from or employ the inventive optical device, aswell as documents made from these materials. The term “documents”, asused herein designates documents of any kind having financial value,such as banknotes or currency, bonds, checks, traveler's checks, lotterytickets, postage stamps, stock certificates, title deeds and the like,or identity documents, such as passports, ID cards, driving licenses andthe like, or non-secure documents, such as labels. The inventive opticaldevice is also contemplated for use with consumer goods as well as bagsor packaging used with consumer goods.

In one such embodiment, the optical device is in the form of a patchembedded in a polymer ID card.

Other features and advantages of the invention will be apparent to oneof ordinary skill from the following detailed description and drawings.Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. All publications, patentapplications, patents and other references mentioned herein areincorporated by reference in their entirety. In case of conflict, thepresent specification, including definitions, will control. In addition,the materials, methods, and examples are illustrative only and notintended to be limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-6 depict a method for forming the image icon arrangement orlayer of one exemplary embodiment of the optical device of the presentinvention.

FIG. 1 is a cross-sectional side view of the optical device before anypigmented material has been incorporated therein;

FIG. 2 is the optical device shown in FIG. 1, where voids in the imageicon layer are shown filled with a first pigmented material and incidentlight in the form of parallel rays is shown impinging on the focusingelement arrangement normal to its surface;

FIG. 3 is the optical device shown in FIG. 2, where uncured firstpigmented material has been removed from the image icon layer leavingonly the cured first pigmented material and the original icon structurebehind;

FIG. 4 is the optical device shown in FIG. 3, where recreated voids areshown filled with a second pigmented material, and collimated light isshown impinging on the focusing element arrangement at a different cureangle;

FIG. 5 is the optical device shown in FIG. 4, where the uncured secondpigmented material has been removed from the image icon layer leavingthe cured first and second pigmented materials and original iconstructure behind; and

FIG. 6 is the optical device shown in FIG. 5, where recreated voids areshown filled with a third pigmented material, and non-collimated(scattered) light is shown impinging on the focusing elementarrangement.

FIG. 7 is a cross-sectional side-view of the exemplary embodiment of theoptical device of the present invention prepared in accordance with themethod depicted in FIGS. 1-6. The device has three different fillmaterials, two of which were directionally cured;

FIG. 8 is the optical device shown in FIG. 7, showing an observerviewing the device from the first cure angle;

FIG. 9 is the optical device shown in FIG. 7, showing an observerviewing the device from the second cure angle; and

FIG. 10 is the optical device shown in FIG. 7, showing an observerviewing the device from a third cure angle.

DETAILED DESCRIPTION

By way of the present invention, a flicker-like optical effect thatoptionally changes color when viewed from different viewing angles isproduced which does not necessarily lie in the plane of the opticaldevice. The inventive optical device may be used in conjunction withlaser engraving allowing for, in at least one embodiment, superior laserengraving through the optical device.

As noted above, the optical device of the present invention comprises atleast one arrangement of image icons formed from one or more curedpigmented materials, and at least one arrangement of optionally embeddedfocusing elements positioned to form one or more synthetic images of atleast a portion of the arrangement(s) of image icons, wherein some orall of the pigmented material(s) is cured using collimated lightdirected through the focusing elements at one or more angles relative toa surface of the optical device (the cure angle(s)) to formdirectionally cured image icons, wherein the synthetic image(s) of thedirectionally cured image icons is viewable at the cure angle(s) andtherefore visually appears and disappears, or turns on and off, as theviewing angle of the device moves through the cure angle(s).

The synthetic image(s), when viewed at the cure angle(s), whether inreflective or transmitted light, may demonstrate one or more of thefollowing optical effects: i. show orthoparallactic movement; ii. appearto rest on a spatial plane deeper than the thickness of the opticaldevice; iii. appear to rest on a spatial plane above a surface of theoptical device; iv. oscillate between a spatial plane deeper than thethickness of the optical device and a spatial plane above a surface ofthe optical device as the device is azimuthally rotated; v. exhibitcomplex three dimensional structures, patterns, movements, oranimations; and/or vi. have in-plane images that appear and disappear,stay static but have dynamic bands of color moving throughout, or areanimated with dynamic bands of color moving throughout.

As described in PCT/US2004/039315 to Steenblik et al., the magnitude ofthe magnification or synthetic magnification of the images as well asthe above-noted visual effects are dependent upon the degree of “skew”between the arrangements (e.g., arrays) of focusing elements (e.g.,lenses) and image icons, the relative scales of the two arrays, and thef-number of the focusing elements or lenses, with the f-number beingdefined as the quotient obtained by dividing the focal length of thelens (f) by the effective maximum diameter of the lens (D).

As also described in PCT/US2004/039315 to Steenblik et al.,orthoparallactic effects result from a “scale ratio” (i.e., the ratio ofthe repeat period of the image icons to the repeat period of thefocusing elements or lenses) substantially equal to 1.0000, when thesymmetry axes of the focusing elements and image icons are misaligned.The appearance of resting on a spatial plane deeper than the thicknessof the inventive optical device results from a “scale ratio” of lessthan 1.0000, when the symmetry axes of the focusing elements and imageicons are substantially aligned, while the appearance of resting on aspatial plane above a surface of the inventive device results from a“scale ratio” of greater than 1.0000, when the symmetry axes of thefocusing elements and image icons are substantially aligned. Theappearance of oscillating between a spatial plane deeper than thethickness of the optical device and a spatial plane above a surface ofthe optical device as the device is azimuthally rotated results fromaxially asymmetric values of the scale ratio (e.g., 0.995 in the Xdirection, and 1.005 in the Y direction).

The image icons used in the practice of the present invention, which areprepared using one or more cured pigmented materials, may be made in theform of posts, or in the form of voids or recesses on or within asurface of the inventive optical device. The posts may be prepared fromthe cured pigmented material(s), or the areas surrounding the posts orthe voids or recesses may be either coated or partially or completelyfilled with the pigmented material(s). While the size, form and shape ofthe icons are not limited, these raised or recessed icons may assume theform or shape of, for example, positive or negative symbols, lettersand/or numerals that may be visually detected and possibly machinedetected or machine read. They may also constitute bas-relief structuresthat give a three-dimensional effect, or composite or mosaic-like imagesformed by a plurality of spaced apart, raised or recessed icons that maytake the form of lines, dots, swirls, or combinations thereof. In onecontemplated embodiment, the image icons used in the practice of thepresent invention are raised or recessed icons having a height or recessdepth ranging from about 0.5 to about 8 microns.

As noted above, embodiments are contemplated in which two or more typesof image icons (e.g., micro- and nano-sized image icons) are in registerwith one another within one arrangement or layer of image icons withinthe inventive device. For those embodiments, a form of preferred curingis required. One form of preferred curing, contemplated by way of thepresent invention, is differential dissolution of the fill, which may beaccomplished using structures of different size and fills of differingsolubility. This may be combined with collimated curing to producedifferent structures with different compositions on a single layer.Collimated curing may also be used alone as a means for producing suchsingle layers of multifunctional micro- and/or nano-sized image icons.

Pigmented materials contemplated for use in the present inventioninclude, but are not limited to, pigmented resins and inks. In anexemplary embodiment, a sub-micron pigment in the form of a pigmentdispersion, which is available from Sun Chemical Corporation under theproduct designation ‘Spectra Pac’, is used. To this pigment dispersionis added other curable (e.g., ultraviolet (UV) curable) materials andphotoinitiators so as to achieve a curable pigmented material suitablefor use in the present invention. The resulting curable pigmentedmaterial is then used to prepare the posts, or to fill the voids (orrecesses) and/or the regions surrounding the posts.

The optionally embedded focusing elements used in the practice of thepresent invention include, but are not limited to, refractive focusingelements, reflective focusing elements, hybrid refractive/reflectivefocusing elements, and combinations thereof. In one contemplatedembodiment, the focusing elements are refractive microlenses. Examplesof suitable focusing elements are disclosed in U.S. Pat. No. 7,333,268to Steenblik et al., U.S. Pat. No. 7,468,842 to Steenblik et al., andU.S. Pat. No. 7,738,175 to Steenblik et al., all of which are fullyincorporated by reference as if fully set forth herein.

Embedment of the focusing elements serves to improve the inventiveoptical device's resistance to optically degrading external effects. Inone such embodiment, the refractive index from an outer surface of theinventive device to refracting interfaces is varied between a first anda second refractive index, the first refractive index beingsubstantially or measurably different than the second refractive index.The phrase “substantially or measurably different”, as used herein,means a difference in refractive index that causes the focal length(s)of the focusing elements to change at least about 0.1 micron.

The embedding material may be transparent, translucent, tinted, orpigmented and may provide additional functionality for security andauthentication purposes, including support of automated currencyauthentication, verification, tracking, counting and detection systems,that rely on optical effects, electrical conductivity or electricalcapacitance, magnetic field detection. Suitable materials can includeadhesives, gels, glues, lacquers, liquids, molded polymers, and polymersor other materials containing organic or metallic dispersions.

The optical device of the present invention, in an exemplary embodimentin which the focusing elements are microlenses and each image icon inthe arrangement(s) of image icons is formed from one cured pigmentedmaterial, may be prepared by: (a) applying a substantially transparentor clear radiation curable resin to upper and lower surfaces of anoptical spacer or spacer layer; (b) forming a microlens array on theupper surface and an icon array in the form of voids (or recesses)and/or posts on the lower surface of the optical spacer; (c) curing thesubstantially transparent or clear resin using a source of radiation;(d) filling the icon array recesses and/or areas surrounding the postswith one or more pigmented materials; (e) removing excess pigmentedmaterial(s) from the lower surface of the optical spacer; and (f) curingsome or all of the pigmented material(s) using collimated (madeparallel) light directed through the focusing elements toward the iconlayer at one or more angles relative to a surface of the optical device.

The curing of the pigmented material(s) involves directing collimatedlight from a collimated light source through the microlens array towardthe icon array such that the resulting light impinging on the arraycauses curing of the pigmented material(s). Suitable collimated lightsources include laser light, light (e.g., sunlight, UV light, infrared(IR) light) directed through one or more collimating lenses, through anarrow slit, toward a parabolic reflector, from a more directionalsource such as an array of LEDs, or combinations thereof. In onecontemplated embodiment, the collimated light source is a UV lithographyexposure unit.

Referring now to the drawings in detail, FIGS. 1-6 depict a method forforming the image icon arrangement or layer of one exemplary embodimentof the optical device of the present invention. In FIG. 1, across-sectional side view of the optical device before any pigmentedmaterial has been incorporated therein is shown generally at 10. Device10 basically comprises: (a) an arrangement of focusing elements 12; (b)a base film or optical spacer 14; and (c) a partially formed image iconlayer (i.e., original icon structure) 16 prepared from a substantiallytransparent or clear radiation curable resin 18 with icon recesses orvoids 20 therein.

In a first step of the method for forming the image icon arrangement orlayer, which is shown in FIG. 2, the voids 20 are filled with a firstpigmented material 22. Incident light 24 in the form of parallel raysimpinges normal to the surface of the focusing element arrangement 12.In other words, the parallel rays come in at an angle equal to zero.Each focusing element focuses its respective incident light onto theimage icon arrangement or layer, with the focusing occurring at theapproximate focal distance of the focusing element. The areas of thefilled voids that are very close to the focal points are cured. Theareas of the filled voids that are not near a focal point will not becured.

The uncured first pigmented material 22 is then removed (e.g., washedaway) leaving, as best shown in FIG. 3, only the cured first pigmentedmaterial 26 and the original icon structure 16 behind. This steprecreates voids 20 in the image icon arrangement or layer.

In the next step, the recreated voids 20 are filled with a secondpigmented material 28. A different cure angle is chosen, and collimatedlight 30 is produced that comes from that angle. As shown in FIG. 4, thecure angle is coming from the upper-right of the surface of the device10. The collimated light 30 consists of all parallel rays. As before,some of the voids 20 are very close to the focal points of the focusingelements, and the second pigmented material 28 in those zones is cured.Some of the pigmented material 28 is not exposed because it is not closeto a focal point and so it remains uncured.

The uncured second pigmented material 28 is then removed leaving, asbest shown in FIG. 5, the cured first pigmented material 26 and curedsecond pigmented material 32 and the original icon structure 16 behind.Again, this step recreates voids 20 in the image icon arrangement orlayer.

In the next step, the recreated voids 20 are filled with a thirdpigmented material 34. As shown in FIG. 6, the material is cured usingnon-collimated (scattered) light 36. As a result, there is no effectivefocusing by the focusing elements, and the entire icon layer is exposed.Effectively this ensures that all of the third pigmented material 34 iscured.

One or more of the method steps involving the filling of the voids witha pigmented fill material may be performed using an unpigmented materialthat is designed to not absorb laser light. This provides “vacant” iconspaces, the benefits of which will be discussed further below.

The optical device prepared in accordance with this method is shown inFIG. 7 and marked with reference number 100. There are three differentcured pigment materials 26, 32, 38 (cured third pigmented material) inthis case, two of which (26, 32) were directionally cured.

Referring now to FIG. 8, an observer, who is viewing the device 100 fromthe first cure angle, sees the synthetic image(s) associated with thecured first pigmented material 26. In FIGS. 8-10, the observer is “veryfar away” from the device such that the observer's effective angle toeach of the focusing elements in FIG. 8, for example, is equivalent tothe first cure angle. The synthetic image(s) associated with the curedfirst pigmented material 26 is only visible from the first cure angle.

An observer, who is viewing the device from the second cure angle (seeFIG. 9), sees the synthetic image(s) associated with the cured secondpigmented material 32. This synthetic image(s) is only visible from thesecond cure angle.

An observer, who views the device from an angle which is not one of thecure angles (see FIG. 10), sees the synthetic image(s) associated withthe cured third pigmented material 38. This synthetic image(s) isvisible from any angle that is not equivalent to the first cure angle orthe second cure angle. In some cases, especially those in which theoptical device or system has a large f-number, an observer may view thedevice from a high angle (i.e., an angle far from the “normal” angle).As the viewing angle becomes high enough, the line of sight through afocusing element will begin to see the image icons that are underneathan adjacent focusing element. In this type of situation, an observer maysee one or more synthetic images associated with a specific cure angleat an angle other than the specific cure angle.

The optical spacer or spacer layer may be formed using one or moreessentially transparent or translucent polymers including, but notlimited to, polycarbonate, polyester, polyethylene, polyethylenenapthalate, polyethylene terephthalate, polypropylene, polyvinylidenechloride, and the like. In an exemplary embodiment, the optical spaceror spacer layer is formed using polyester or polyethylene terephthalate.

It is noted that while the use of an optical spacer or spacer layer ismentioned in the above exemplary embodiment, the optical device of thepresent invention may also be prepared without an optical spacer orspacer layer.

Suitable radiation curable resins include, but are not limited to,acrylics, epoxies, polyesters, acrylated polyesters, polypropylenes,urethanes, acrylated urethanes, and the like. Preferably, the arrays areformed using an acrylated urethane, which is available from LordChemicals.

As previously mentioned, image icons formed from two or more pigmentedmaterials may be prepared by curing each material with collimated light,or by curing one material with collimated light and another materialwith another means for curing (e.g., radiation curing, chemicalreaction). Synthetic images of the image icons formed from suchdirectionally cured pigmented material(s) would be viewable at the cureangle(s), while synthetic images of the image icons formed from thenon-directionally cured pigmented materials would be viewable over awide range of angles. It is noted that the arrangement(s) of image iconsused in the practice of the present invention may also include prior artimage icons formed in their entirety from non-directionally curedpigmented materials.

In one such exemplary embodiment, each image icon in the arrangement(s)of image icons is formed from two cured pigmented materials, each havinga different color. Here, each pigmented material is cured usingcollimated light at an angle through the focusing elements that isdifferent from the angle used to cure the other pigmented material. Inparticular, this exemplary embodiment may be produced by curing acolored pigmented material using collimated light from one angle,washing the uncured pigmented material from the device, and then addinga second colored pigmented material and curing it at a different angle.The resulting optical device will project a synthetic image(s) of afirst color that is viewable at the first cure angle, and a syntheticimage(s) of a second color that is viewable at the second cure angle. Aswill be readily appreciated, a large number of different color pigmentedmaterials could be added this way. Additionally, another different colorpigmented material is added that is cured without using collimatedlight, to provide a “background color” that can be seen from any anglethat has not already been used for angular curing.

In another such exemplary embodiment, each image icon in thearrangement(s) of image icons is formed from one cured fluorescentpigmented material and from one cured non-fluorescent pigmentedmaterial. Here, the fluorescent feature, which is detectable only at agiven angle but not at another given angle, may serve as an effectivemachine readable authenticating feature.

In a further exemplary embodiment of the present invention, the opticaldevice is a laser markable optical device that basically comprises theoptical device described above, and optionally one or more layerslocated above and/or below the optical device, wherein at least onearrangement or layer of the optical device or at least one layer aboveor below the optical device is a laser markable arrangement or layer.

The term “laser markable” or any variant thereof, as used herein, isintended to mean capable of physical or chemical modification induced orformed by a laser including, but not limited to, carbonizing, engraving,engraving with or without color change, engraving with surfacecarbonization, color change or internal blackening, laser marking bycoating removal, ablation, bleaching, melting, swelling, andvaporization, and the like.

In a preferred embodiment, the inventive laser markable optical devicehas: (a) an arrangement of optionally embedded focusing elements (e.g.,embedded refractive focusing elements) and an arrangement of image iconsthat are separated by a laser markable layer that also functions as anoptical spacer; and/or (b) one or more laser markable layers locatedbelow the optical device.

In the above preferred embodiment, which may be used in embedded lensand other ID products (e.g., a patch embedded in a polymer ID card),personalized data in the form of static two dimensional (2D) imageswould be laser engraved into or below the optical device at an anglethat differs from the angle(s) at which the collimated curing energy wasapplied.

In the latter embodiment where one or more laser markable layers arelocated below the optical device, the arrangement of image iconscontains “vacant” icon spaces. As previously mentioned, the “vacant”icon spaces are prepared using unpigmented material(s) designed to notabsorb laser light (e.g., UV curable mixtures). The unpigmentedmaterial(s) in this embodiment is directionally cured at the same anglethat a laser engraver would use to write the static 2D images. Theremainder of the icon recesses or voids in the arrangement of imageicons are filled with pigmented materials cured at angles other than theangle used to cure the unpigmented material(s).

By way of this embodiment, laser energy is allowed to pass through theoptical device with little laser energy being absorbed thereby, whichprovides for superior laser engraving through the optical device.

The present inventors have discovered that certain pigmented materialswill absorb laser energy when an attempt is made to laser engravethrough the optical device. The result is a defective laser-marked darkimage with white or missing areas. This problem can be avoided bycarefully choosing which pigments to use, or by employing theabove-mentioned “vacant” icon spaces. As will be readily appreciated bythose skilled in the art, the use of “vacant” icon spaces allows for theuse of any pigment without the concomitant risk of forming defectivelaser-marked dark images.

The net effect of the above-referenced embodiment is that the colored,pigmented synthetic image(s) would not be visible at the same angle thatthe static 2D laser engraved image(s) is visible. This means that therewould be no pigment in the areas whether the focusing elements tend tofocus the laser from the laser engraver, and the risk that the pigmentedmaterial(s) would absorb the laser energy is avoided.

As alluded to above, to mark the laser markable optical device of thepresent invention, light energy from an engraving laser would be focusedby the focusing elements and would engrave a laser markable layer insuch a way that an image would be formed in the laser markable layerthat is only viewable from the engraving angle. This technique allowsfor greater customization of the inventive device with a dynamic,personalized image that can be made to appear and disappear. Multiplelaser marking angles can be used in the same device thereby providingmultiple images, each of which is observable from a different viewingangle. In this way, short animations or changing images can be made in apersonalized way. By way of example, when such a device is used on or inconjunction with an ID document, a small version of the portrait usedfor the ID document could be made to turn on and off. This dynamicportrait displayed by the inventive device would be unique to the IDdocument and would increase the security of the document.

The resulting laser marked optical device would have one or more lasermarked static 2D images on the laser markable layer(s). Here, the term“laser marked” or any variant thereof is intended to mean carrying ordisplaying any mark formed by a laser or laser-like device.

Suitable laser markable layers may be prepared using thermoplasticpolymers. In a first category, thermoplastic polymers with goodabsorption and carbonization may be used. These polymers are lasermarkable in the absence of so-called laser additives, which arecompounds absorbing light at the wavelength of the laser used, andconverting it to heat. Examples of these polymers, which produceextensive blackening in the area exposed to the laser, includepolyethersulfone (PES), polysulfone (PSU), polycarbonate (PC), andpolyphenylene sulfide (PPS). In a second category, thermoplasticpolymers with laser additives (e.g., pigments or special additives) maybe used. Examples of these polymers, which can be marked uniformly andwith good quality, include polystyrene (PS), styrene acrylonitrile(SAN), acrylonitrile butadiene styrene (ABS), PET, PETG, polybutyleneterephthalate (PBT) and polyethylene. Examples of these laser additivesinclude carbon black, antimony metal, antimony oxide, tin-antimony mixedoxides, phosphorous-containing mixed oxides of iron, copper, tin and/orantimony, mica (sheet silicate) coated with metal oxides. The lasermarkable layers have preferred thicknesses ranging from about 5 to about500 microns, more preferably from about 25 to about 200 microns.

In a preferred laser marking technique, a V-Lase 10 Watt Q-switched 1064nanometer (nm) laser marking system is used to mark the inventive lasermarkable device, the laser marking system producing laser light emissionat a setting of 30,000 Hertz (Hz). The laser marking system is set to80% of maximum power, and a scan speed of 200 millimeters per second(mm/sec). These settings produce a high contrast mark in the desiredlocation within the inventive laser markable device without burning oroverexposure.

As alluded to above, the present invention also provides sheet materialsand base platforms that are made from or employ the inventive opticaldevice, as well as documents made from these materials. The inventiveoptical device is also contemplated for use with consumer goods as wellas bags or packaging used with consumer goods.

By way of example, the inventive optical device can be utilized in avariety of different forms (e.g., strips, patches, security threads,planchettes) with any banknote, secure document or product forauthentication purposes. For banknotes and secure documents, thesematerials are typically used in the form of a strip, patch, or threadand can be partially embedded within the banknote or document, orapplied to a surface thereof. For passports or other ID documents, thesematerials could be used as a full laminate or inlayed in a surfacethereof. For product packaging, these materials are typically used inthe form of a label, seal, or tape and are applied to a surface thereof.As noted above, in one exemplary embodiment, the optical device is inthe form of a patch embedded in a polymer ID card.

What is claimed is:
 1. An optical device that produces flickeringoptical effects, the optical device comprising: an icon layercomprising: a radiation curable resin, at least one arrangement ofdirectionally cured image icons, each directionally cured image icon ofthe at least one arrangement of directionally cured image iconscomprising a region of one or more directionally cured pigmentedmaterials disposed in or on the radiation curable resin, the region ofone or more directionally cured pigmented material formed as one or moreof a void or post formed in the radiation curable resin; and at leastone arrangement of focusing elements positioned relative to the at leastone arrangement of directionally cured image icons to form one or moresynthetic images of at least a portion of the at least one arrangementof directionally cured image icons, wherein some or all of the one ormore directionally cured pigmented materials are directionally curedbased on a direction of a collimated light directed through focusingelements of the at least one arrangement of focusing elements at one ormore collimated light cure angles, wherein the one or more syntheticimages of the directionally cured image icons is viewable at the one ormore collimated light cure angles and visually appears and disappears,or turns on and off, as a viewing angle of the optical device movesacross a range of viewing angles.